A few decades ago, in an attempt to reduce the number of eye injuries, the FDA was charged with enforcing new regulations governing plastic lenses used in eyeglasses. Among these regulations, 21 CFR §801.410 sets out an impact resistance requirement and test method which involves dropping a ⅝ inch steel ball onto the finished or uncut finished lens from a height of 50 inches (commonly referred to as the “Drop Ball Test”). With regard to plastic lenses, 21 CFR §801.410 allows statistical batch testing to be completed on a batch basis by the lens manufacturer. This testing is typically performed on a daily/per batch basis.
At the time 21 CFR §801.410 was introduced, lens technology was fairly simple. Accordingly, lens manufacturers and not downstream processors took responsibility for assuring lens compliance with 21 CFR §801.410. Over the ensuing years, lens technology grew increasingly complex. Numerous new plastics, other refractive materials, and hard coats became available. New methods of curing lenses and hard coats, and of applying anti-reflective treatments and other lab-applied treatments came into use. As the number of materials, treatments, and equipment increased in the field, it became increasingly difficult for lens manufacturers to guarantee compliance with 21 CFR §801.410 for all of the combinations of treatments on the same lens. As a result, lens manufacturers more frequently place the burden of impact compliance proof on subsequent processors.
The FDA recommends that lens manufacturers and subsequent processors use the ANSI/ASQ Z1.4 sampling plan which is an acceptance sampling system to be used with switching rules on a continuing stream of lots for Acceptance Quality Limit (AQL) specified. Use of the ANSI/ASQ Z1.4 sampling plan, however, requires such a large sample size that the sampling plan becomes economically unfeasible for the manufacturer. Manufacturers using the ANSI/ASQ Z1.4 sampling plan typically spend $80,000 to 130,000 per year to perform the testing. Therefore, a standard, affordable methodology by which laboratories, manufacturers, and importers can assure that their products comply with the minimum performance requirements set forth in 21 CFR §801.410 is highly desirable.